In large electric generating stations, the generator is the mechanism or machine that most likely converts (various forms of input energy) water, oil, nuclear or other mechanical energy to deliverable electrical energy. That energy is intended to be ultimately converted and transported to consumers (factories, substations, businesses, buildings, residential home consumers, etc.). Before being transmitted, the electrical energy of the generator is first passed to a step-up transformer. Usually, the safe, rugged connection between the generator and the step-up transformer is known as the Isolated Phase Bus (also known as “Iso Phase Bus,” or “IPB”). Isolated Phase Bus is a custom designed electrical pathway carrying very high amperage (the output production of the generator) and safely delivers it to a large step-up (step up in terms of voltage and down in terms of amperage) transformer, usually located in the power plant's adjoining switchyard. That transformer “re-packages” the electrical power (by stepping up the voltage and thereby commensurately lowering the amperage) to be delivered to a myriad of distribution substations for ultimate delivery to customers throughout the servicing area.
The Iso Phase Bus gains and retains its robustness by performing three important functions. It separates each of the three (3) phases of electrical power into their own mechanically ridged conducting paths; it safely protects that ridged conducting path with a surrounding, electrically grounded rigid metal enclosure; and it separates each of those three grounded metal enclosures with an air gap for further electrical isolation from electrical faults.
From a mechanical and visual perspective, an Iso Phase Bus is a high conduction, thick-walled metal “pipe” (called the conductor) within a larger diameter, yet thinner walled outer “pipe” (called the enclosure). As both the conductor and enclosures are preferably cylinders, long and tubular, the term “pipe” is generically and visually appropriate; however, unlike a traditional pipe, the conductor and enclosure are not configured to convey water, other fluids, or gases. Both the conductor and enclosure are preferably manufactured from high conductivity aluminum. Engineering constraints require that both conductor and enclosure must be able to properly handle the same amount of current, and therefore the center conductor pipe—which has a relatively smaller diameter—will preferably have a thicker material wall dimension (preferably around ½″ thick), while the outer thinner walled enclosure—which has a larger pipe-like diameter—can mathematically have the same amount of total metallic material per unit length yet with a thinner wall thickness (preferably around ¼″). The conductor is preferably held in the center of the enclosure by rigidly mounting a non-conducting “stand-off” insulator inside the cylindrical enclosure that allows and maintains the conductor to sit on top of the insulators in the center of the enclosure. Some manufacturers use two or three concentric, ring-like insulator designs to hold the conductor in a substantially centered position within the enclosure.
Throughout the industry, the overall length from generator to step-up transformer (of ¼″ thick, outer aluminum cylindrical-enclosures) is developed by fabricating numerous segments, each up to but not longer than about 6 feet in length. Then coupling theses numerous segments together end to end via welding. Generally two opposing edges of these pipe-like segments are held end to end and one or more bands (a/k/a—weld backing strips) are placed across the interior or exterior of this “butted together joint.” Initial tack welding of the interior or exterior “weld backing strip(s)” holds these pieces and/or adjacent sections together.
The reason for this 6′ segmented length of end to end couplings to create the overall length of piping from generator to step-up transformer is due to the methodology of the sheet metals fabrication process and dimensional limitations of over-the-road transportation systems. Aluminum is generally produced into large ingots (or shapes suitable for further processing) in smelting mills. To make a useful end product—one of the next steps is for those large ingots to be conveyed to rolling mills where they are then rolled into long, flat, ribbons of material of ever-decreasing thicknesses and corresponding increasing in width and length (as the volume stays the same). For material thicknesses preferably ranging from very thin up to approximately ½″ of thickness, the flat, planar, ribbon-like material comes down a long line in the rolling mill and is then coiled onto an appropriately sized center tube (think aluminum foil). As a direct consequence of the maximum widths for trucks on the US highways, it is current industry practice to make these rolls or sheets of aluminum, up to, but usually not much bigger than, 2 meters wide. Therefore using manufacturers of the above mentioned “rolls or sheets of aluminum” are generally working with a maximum width of approximately six (6) feet. Aluminum can be pulled off of the roll for any desired length, but the material's thickness has been fixed by the rolling process and that width has been fixed to be no greater than approximately 6 feet—again due to transportation and handling limits.
Taking a length of flat sheet aluminum material off of the transported aluminum coil and rolling that piece into a tube will produce a section with the mathematical diameter of said tube being the well-known circumference of the flat sheet's length (the dimension entering the rolling machine)—divided by Pi (3.14 . . . ). That means that if the aluminum coming off the roll is preliminarily fixed in its width dimension at six (6) feet wide (due to the road restrictions of wide trucks) the largest diameter tube which can be made from the 6 foot dimension is just under 23 inches (6 feet divided by 3.14 . . . =22.9 . . . inches). Generally, outer enclosures of Iso Phase Bus have preferred diameters being substantially larger in diameter than 23 inches. This can then be accomplished with a sheet unrolled from the aluminum coil which is longer than the 6 feet width of said aluminum coil. The properly engineered prescribed length requires the sheet that is to be unrolled from the aluminum coil to be calculated by multiplying the final desired diameter for the enclosure cylinder section by Pi. (ex—a section requiring a four foot diameter (48 inches) requires a length of uncoiled sheet of aluminum to be (48 inches×3.1417 . . . =) or about 150.80 inches. Iso Phase Bus fabricators therefore make enclosure sections with diameter dimensions as necessary by uncoiling sheets from the 6 foot wide roll at properly engineered, prescribed desired lengths. However, since the planar material is coming from a 6 foot wide coil of aluminum, the maximum length of the tubular enclosure after it is rolled will be no longer than the 6 foot which was the width of the aluminum coil.
An electrical generator and its associated step-up voltage transformer are generally over a hundred feet apart. This requires the three separate phases of Iso Phase Bus “pipes” or cylinders of aluminum enclosures to be possibly hundreds of feet long. These custom lengths are fabricated by taking the above mentioned six-foot tubular segments and butting them end to end together, one after another. These “butt joints” can then be solidly welded together, continuously around their entire mating circular perimeters. Generally, this welding together process can be done in one of two ways, described in more detail below. Butt joint welding of aluminum Iso phase or tubular section after section, eventually creates a single, lengthy, and continuous pipe of sufficient length which follows the proscribed path from Generator to Step-up Transformer and any associated tap-off points.
The methods currently used in the art for joining adjacent tubing sections using “butt joints” at the circular edges allow the two pipes to rotate and “wiggle” somewhat during the connection process. This is unavoidable and undesirable. This rotation and wiggling means that the two sections are not precisely maintaining their alignment during the butt welding process such that they are not axially and circumferentially aligned and true as desired. The alignment of the longitudinal axis of one pipe or tubular cylinder to the adjacent tubular cylinder is highly desirable in IPBs. It is a key characteristic that is vital for IPB fabrication and in field erection. Therefore, today, using conventional butt welding, unnecessary energies must be allotted to ensure straightness is maintained when adjoining sections via butt welding/joining and, in any event, the longitudinal axial alignment is not as precise as desired. Generally, the butt welding is done by using internal or external, originally separate, backing strips which encircle the outside of the adjoining or abutting edges of the two pipe segments or are wrapped into the inside of the adjacent pipe-like segments. These are intended to wrap around (or inside of) the seam between the tubular sections to be welded together and, then, the backing strips welded to the outside (or inside where internal backing strips are employed) of the surface of the cylinders.
The present invention discloses a system, end product and method for rolling metal into large cylinders, as an enclosure for Iso Phase Bus, wherein lengths of the tubular sections can be easily and efficiently adjoined, all while maintaining axial alignment, then welded together. One end of a single tubular or cylinder section will be provided with either a “flare out” or a “stepped in” flange. The other end left without change of diameter. Then, the flare out of one end of a first tubular or cylinder section will be slid over the untreated end of a second tubular section. Alternatively, the inwardly tapered or flared inwardly end of a first end of a tubular section is slid within the untreated end of a second tubular section. The two ends (whether male or female of a first tubular section) cooperate and mate and provide a smooth outer wall for the length of the two cylinders when the same are slid into or over, respectively, the untreated end of a second tubular section. Then, the single seam can be welded together such that a length (of two or more) of the cylinders is created and the longitudinal axis of the multiple adjacent sections are precisely aligned. An enclosure is thus provided of any desired overall length with the seams between adjacent cylinders being welded with a single weld line and with the longitudinal axis being easily maintained and substantially aligned.
According to the present invention, a pinch rolling machine and/or jig or tool is used to “pinch” or taper diametrically inwardly (or a similar machine, jig or tool is used to outwardly flare) one end of each of a set of cylinders. The set of custom machining “pinch rollers” are used such that when properly pressured together, one end of the aluminum tube is rolled between them, smoothly enlarging (for the flared out end) or tapering or reducing the diameter of the end (for the inwardly pinched end or the stepped down end). The flared out end is intended to slide over the untreated end of a second cylinder until the inside shoulder of the flared out end butts against the untreated end or shoulder of an adjacent tubular section. In the other embodiment, the inwardly pinched down or inwardly tapered end, it is slid within the smooth untreated end of the wall of the adjacent second cylinder until the outside shoulder of the inwardly tapered end contacts with the edge of the untreated end of the second cylinder. In either configuration, then, a smooth inside wall of the two cylinders is presented (with the flared out configuration) or a smooth outside wall is provided (where the end of a cylinder is inwardly tapered or necked down and slid within an untreated cylindrical end of the second tube. A single line of welding joining the two segments together is presented. The two cylinders are secured together by the welding and the structure, rigidity and alignment of central longitudinal axis further maintained by the slight overlap of the outside, outwardly flared pipe of one section on the untreated end of a second pipe section or the inwardly stepped in or tapered pipe end of one section being slid within and maintained inside of the untreated end of the second tubular section. This system, end product and method “pinches” preferably approximately one to three inches (+/−) of one of the ends of the aluminum enclosure tubes. The amount of pressure put on the pinch rollers and the time allowed for the cylinder ends to remain within the rollers of the rolling machine is preferably set so that the amount of diameter outward expansion or tapering/flared reduction of the enclosure tube's ends are ever so slightly more than twice the general wall thickness of the tube itself (i.e. the thickness of the aluminum sheet used to create the tube). This amount of diameter change allows the modified end to tightly slide within or over the untreated adjoining section. This process thereby preferably creates a “self-backing” surface for an integral weld on the tube itself for the connection to the next enclosure tube.
Once this pinching in or out of one end of a first tubular section has been accomplished, a second tube—whose free end has not been pinched and rolled—can snugly slide over the pinched or tapered end. Of course, its distal end is provided with either a flared outwardly end or an inwardly pinched down end, or an untreated end, so that it will cooperate and mate with another cylinder. Only untreated ends of cylinders will not be butted together. In the preferred embodiment, all of the first ends of the cylinders for the length required from generator to step transformer are either flared outwardly or tapered inwardly with the other ends untreated. To thus create the proper length of butted together, axially aligned tubular sections, is efficient. Welding secures the pipe sections together, as required.
As stated above, this process self-creates its own welding backing surface and dually auto-aligns the two tubes with exceptional straightness i.e., longitudinal axis of the two tubes are aligned. Auto aligning is a byproduct of the un-flared or untreated tube end being forced against the well-formed “knee” or shoulder of the flared end of an adjacent tube or pipe segment. Using the system and method of the present invention, the end of a first pipe can be pinched either inwardly or flared outwardly from the original outer circumference of the pipe, thereby creating an internal inwardly confined or diameter-squeezed offset flange or an exterior, outwardly flared flange. By creating a flange, either internally or externally, the leading edge of the first pipe is uniformly altered so as to perfectly fit within or over the untreated interior or exterior surface, respectively, of a second pipe with its end having not having been pinched or flared. Thus, the two pipe segments can snugly fit with ends mating with one another, holding firmly in place for being then welded together. This method also increases the common surface area of the ends which are welded or connected. This presents a much-needed improvement to the prior art systems, which attempt to weld two pipes of the same outer circumference (with interior or exterior bands at the joint) which have their untreated ends butt up against one another thereby necessitating maintaining them in place during the welding process. Rather than the butting and welding of the two pipe segments with identical dimensions of their ends, as in the prior art, the present invention allows the pipe segments to easily and securely affix within one another to ensure uniform and proper welding of the same, together with substantially “automatic” axial alignment. This system and method can be used to longitudinally join an unlimited number of pipes, as each pipe can be provided with one pinched or stepped down diameter end or one outwardly flared end and one untreated end. These cylinders can be easily and quickly assembled to provide the length of enclosure required for IPB.
Thus, the present inventive system and method removes the need to create a backing band or bands (or overlying band(s)) for attaching one or more pipe sections/segments, and, also provides substantial auto alignment of two or more pipe segments. The present invention reduces the time to join sections and holds the sections in their proper respective positions so as to allow for quick, efficient and secure welding of the segments together. The present invention offers a superior electrical conduit as there is more surface area contact of actual pipe segment to pipe segment at the ends due to the snugness of the joint—formed by the mating of the cylinders and their formed ends.